Summary Objectives To describe the application of seven core principles to the design and evaluation of a human immunodeficiency virus (HIV) testing social marketing campaign as a case study example. Study design The Centers for Disease Control and Prevention (CDC) used a structured social marketing approach, informed by the Ecological Model, the Theory of Planned Behaviour and the Health Belief Model, to develop and evaluate a two-city campaign with print, radio and outdoor advertising; HIV telephone hotlines; an HIV website; community partnerships; and events to promote information seeking and HIV testing. Methods The CDC applied seven core principles to design and evaluate the campaign, including formative research, the use of behavioural theories, audience segmentation, message design and pretesting, channel selection, process evaluation and outcome evaluation. Results Over 200 partners in both cities contributed significantly to campaign efforts. Key informant interviews indicated that, due to increased coordination, city infrastructures for HIV testing improved. More than 9600 individuals attended campaign events in both cities, with 1492 rapid HIV tests administered and 14 newly-identified HIV individuals. Overall, event attendees responded positively to campaign materials and events, and free HIV testing opportunities. The campaign significantly increased information-seeking behaviours in the form of hotline calls and web searches. Audience reaction and receptivity to the final campaign materials was very high. Exposure to campaign messages was associated with increases in key knowledge items, intentions to get tested, and peer-to-peer communication. Conclusions The seven core principles, including formative research, behavioural theories and extensive partnerships, acted synergistically to help a campaign reach its target audience with compelling, relevant messages and motivate them to seek information and get an HIV test. Rapid testing removes many barriers by providing a testing process that can be accessed and acted upon quickly in response to media exposure. Findings suggest that modifying the campaign in future implementations to encourage the target audience to attend and participate in rapid testing events, while expanding the number and reach of such events, may have considerable potential to measurably increase testing behaviours.